1. Field of the Invention
The present invention relates to variable pneumatic pressure force-transmitting mechanism which includes a flexible pneumatic chamber that is contractable and extensible and that can be contracted without appreciable buckling.
2. Prior Art
The pneumatic pressure mechanism of the present invention is particularly suited for exerting pressure on the barking arms of a mechanical log barker of the type shown in Robbins U.S. Pat. No. 3,190,327 or Smith U.S. Pat. No. 3,137,329 for example.
Each of the pneumatic actuators for a barking arm of the Robbins patent log barker includes a sectorshaped pneumatic chamber through which swings a rectangular vane that is connected to the barking arm. It is difficult to seal the edges of such vanes relative to the walls of the pneumatic chamber.
The barking arm actuators of the Smith patent include pneumatic chambers in the form of hoses that bear on shoes connected to the barker arms, but such pneumatic chambers are capable of only very limited change in volume for moving such shoes and the hoses undoubtedly would be subject to quite rapid fatigue.
Flexible pneumatic chambers of generally circular cross section which can be contracted and extended have been used for various purposes but they have not been suitable for use under conditions where they would be susceptible to excessive buckling during contraction because the resultant repeated deformation during use would cause rapid fatigue.